Lamp



1,634,528 y w. H. WOOD Filed July 13, 192.5 2 Sheets-Sheet 1 Wznugm H. Wooo HMW 1,634,528 July 5,1921, WHWOOD LAMP Filed July 13 1,92 2 Sheets-Sheet z Pig. 17 1 am N l W18 ,Pie 9 I I wnum H.Woob

. ATTORNEYS waists PATENT OFFICE.

I D, or sense nucran, .ogio,

Application .flcrl an is, v1925. seal in. 43,159.

- This invention relates to lamps and has foran improved type its object the provision of of projecting lamp for vehicle use, such as automobiles, motor trucks. aeroplanes, etc, which shall be more easily iocussed than other lamps; which shall afford an improved distribution of the light; which shall permit larger tolerance-in manufacture: which shall be more easily manufactured and less 10 liable to manufacturing imperfections; while further advantages and objects will become apparent as the description proceeds.

In the drawings accompanying. and forming a part of this application I have shown certain preferred physical "forms in which my inventive idea can be embodied. although itwill be understood that these have been selected merely for illustrative purposes out of a great number of possible shapes and ar- 2B rangements which can equally be employed within the scope of my invention and hence are not limiting upon me. Figs. 1 and 2 are longitudinal sectional views taken at rightangles to each other throuah a spot-light comprising my invention; Fig. 3 is an en lar ed plan view of one type of the lamp bulb shown in Figs. 1 and 2; Fig. i is a similar View of a modified type of lamp bulb which. gives the same result: Fig. 5 is a side elevation of the lamp bulb shown in Fig. 3; Fig. 6 is an end elevation of the'lamp bulb shown in Fig. 3: Fig. 7 is an end elevation of the lamp bulb shown in Fig. 4: Fig. 8 n is a diagrammatic view showing the light pattern produced thereby; Fig. 9 is a side elevation of a head lamp embodying my invention; Fig. 10 is a' front elevation of the lamp shown in Fig. 9: Fig. '11 is ayertical section through a headlight lens which may be used with certain forms of my invention; Fig. 12 is a sectiohalview through another head lamp embodying my. improvements: Fig. 13 is a view of the light field produced by the devices of Figs. 9 (0'12 inclusive: Figi4 is a top plan view of a lamp bulb shown in Fig. 12; Fig. 15 is a side elevation of the fig: Fig. 16 1s a.

lamp bulb shown in Fig. front elevation of the lamp bulbshown in E Fig. 12; Fig. 17 is a front elevation .of'a

side elevation of. a filament mandrel. showjance of the material that the cross section of the strand also i an influence upon its dimensions.

modified form of a lamp bulb; Fig. 18 is a ing the filament thcreong'and Fig. 19 is a cross section of the filament and mandrel.

My improvedlamp is based upon the peculiar operation of a. particular lamp bulb which I have invented when used in 'com hinaticn with a headlight reflector which has a focal point and an axis. namely a spherical surface or a paraboloid 01' one having paraboloid segments. said lamp bulb bearing a certain predetermined relation to the and focal point ofsaid reflector. Said lamp bulb is characterized by having its filament wound into a helix whose cross section is markedly oblong so asto exhibit a substantial length and breadth combined with a thickness which is much less and is preferably substantially negligible. In this way the liszht source. instead of taking the form of a loop, or hairpin. or V. or bar asheretofore customary. exhibits the form, substantially. of a segment of a geometric plane.

Such a filament is much more easily made than almost. any other form. It is' made from a strand 1 of metallic ribbon of wire (so far as concerns the present invention the wound with closely adiacent turns upon a thin flat mandrel 2. For practical use i have found a coil having a width of i milliin the act of being wound 7 are cross. section of the strand is unimpoi Cant), I

meters and thickness of 1/2 millimeter very satisfactory. although other dimensions can be employed. and the desired. although I have found from 5 to 6 millimeters a very satisfactory dimension. The number of turns of the strand within the limits of. this coil depends entirely upon the cross section, length.

and voltage for which it is designed. l have had successful results with a tantalum ribbon 1/2000th inch in thickness and 15 /100th inch wide and makingabout 5 turns; but a tungsten strand because of its lower specific resistance requires different dimensions and lhave also discovered has This filament is mounted inside a glass globe 3 1n .theusu'almanner, its ends suitably joined to still leading-in wires 4-4 and specific resistlength of the coil axially thereof can be as great-ores little as ice is also a considerable degree of latitude permissible in the relation between this filament and the globe axis. In the forms shown in Figs. 1 to 7 inclusive this filament is mounted with its plane parallel to and including the axis aa of the bulb; and the forward end of the globe, which-is pref- I erably hemispherical .as shown in Figs. 3,

" 4, and 5, has its center of curvature b preferably coinciding substantially with the geometrical center of this coil in order to revent the occurrence of any image-g are. This type of lamp bulb is exceedingly satisfactory for searchlights, although when driven with the plane of the filament horizontal it is also useful as a headlight, and affords the same-light pattern as those devices which are at the present day most extensively employed, namely the Ford vertically ribbed lens or the so-called .Flatlite reflector; but in addition my device exhibits the. advantage of a substantially indifferent focus and a very broad range of manufacturing tolerance. I

When sucha bulb is mounted in a paraboloid reflector 10, the bulb. a'xis coinciding with the reflector axis a-a and the focal point f thereof substantially coincidin with the point 6 (see Figs. 1 and'2), a1 rays .rising at the focal point falling on the reflector will be reflected forwardly parallel to the axis as indicated at :11, w; all rays originating at the forward margin of the reflector will be converged after reflection as shown at g and all which originate i the rear edge of the filament will be diverged as shown at 2-2. Considered in a horizontal plane the separation between the points y and z is comparatively small, while considered in the horizontal plane as in Fig.

2 the'.separation of the points y and z is very great. Accordingly there is produced a light field which is much elongated laterally but comparatively narrow vertically as shown in Fig. 8, and it will be found that movement of the lamp bulb axially of the reflector has a comparatively small amount of effect on the light pattern, partly because the axial length of the filament is very great compared with such movement and partly because any diminution of the diverging rays zz tends to be new tralized by increase of the rays g which cross the axis to reinforce them (and vice versa); 'As a result a lamp is produced in whichstlle entire field is uniformly illumt nated'tvithifdiflused light-and wherein black spots and ghosts due to improper focusmg, or imperfections in the reflector cannot occur.

It is possible to improve this as a headlight lamp even more by the addition of further expedients to eliminate the extreme means of a warped reflector shown in Figs.

9 and 10; by means of the glass lens as shown in Fig. ,11; or by means of the rearranged filament as shown in Figs. 12 to 17.

In Figs. 9 and 10 I have shown a reflector of the type covered by my Patents Nos. 1,235,275 and 1,235,276.

The reflector is made of a plurality of independent paraboloid portions, such as indicated at 20, 21,

here shown as flared apart and having their marginal portions'connected by inclined side wings 22 between which is mounted a lamp bulb 3 having a filament of the type shown in Figs. 1 to 7 inclusive. The result of such use is the productionof an illuminated field as shown in Fig. 13, the maximum illumination occurring inside the oval A, the beam exhibiting an apex at 'the point 'B. substantial darkness at the points DD and a considerable amount of-light at the points Q-Q. A somewhat similar improvement in distribution is obtained by using in combination with the reflector shown in Figs. 1 and 2 a glass lens 26 as shown in Fig. 11, of the type having prismatic portions 26,, 27 of different angles adapted to" diffuse and direct according to a predetermined,pattern. Such a lens combined with such a reflector and lamp bulb can bemade to afford the pattern shown in Fig. 13.

The same result can be secured without a.

lens and with the paraboloid reflector 15 by modifying the position of'the plane of the filament as shown in Figs. 12 to 17 inclusive,

the axis aa, meets the same at an oblique angle, the center of curvature "b of the glass globe coinciding withthe forward edge of is shown in Fig. 13. This aspect of my invention coincides with that set forth and clalmed in my patent issued April 14, 1925, No. 1,533,360.

Viewed from above such last described i lamp bulb appears as shown in Fig. 14. It

wherein the filament 1. instead of containing n messes can either run straight from side to side or be bent into V shape as shown in Fig. 17 In either case the filament consists of a flat lattice defining andconiined'within substantially a single plane, which plane is oblique to the reflector axis and intersects the sam substantially at the focal point.

The fiat thin shape or the filament produces exactly the type of light beamnlost usefully employed with a paraboloid reflector. This shape is also advantageous in manufacturing for two reasons first, because of its comparatively great width it is possible to acid as in the case of the e wire mandrels; and, second, because the angular shape of the mandrel holds the strands ti htly thereon and the filament, when woun ,ex-

make a mandrelwhich is used, over and over instead of beinldestroyed by.

than when it is wound on a cylindrical mandrel.

Having thus described my invention what l claim is:-.

The-comb'nation with a reflector having a substantially horizontal axis and a focal point, of an incandescent lamp bulb having afilament consisting of a metallic strand wound in a closely adjacent serie'sof oblong turns producing a flattened helix which exhibits substantial: length and breadth combined with a comparatively small thickness and defines a plane which is symmetricall arranged relative to the vertical plane whic includes said axis.

In testimony whereof I hereunto affix my signature. p v Y WILLIAM H. WOOD. 

